The present invention relates to a reference voltage generating device. More to particularly this invention relates to a reference voltage generating circuit which is controlled by a power control signal.
Description of the Prior Art
There is a reference voltage supply circuit for providing reference voltage for an external circuit. The Japanese Patent Application Laid-Open No. HEI 4-252312 discloses a reference voltage generating device in order that it causes rise time to expedite at the time of applying of reference voltage. FIG. 1 is a constitution view showing one example of a conventional reference voltage generating device. In FIG. 1, a resistor R.sub.1 and a first capacitor Ci are always connected in a series in between a reference voltage output line A of a reference voltage generating source 1 and a power source V.sub.DD. A second capacitor C.sub.2 is always connected in between the reference voltage output line A and ground. Thereby, it causes a reference voltage output V.sub.0 at rise time of the power source to rise rapidly to a voltage value which is settled from the ratio of combined impedance of the resistor R.sub.1 and the first capacitor C.sub.1 to an impedance of the second capacitor C.sub.2, thus it causes the time to shorten when the reference voltage output V.sub.0 rises until the reference voltage which is of the object. A low pass filter (LPF) is constituted by the resistor R.sub.1 and the first and the second capacitors C.sub.1, C.sub.2, thus it causes high-frequency noise to remove. The high-frequency noise comes wraparound to the reference voltage output terminal A from the power source.
In the above reference voltage generating device, since the low pass filter (LPF) consisting of the resistor R.sub.1, the first and the second capacitors C.sub.1, C.sub.2 are always connected in between the power source V.sub.DD and the reference voltage output terminal A after rising of the power source, in some circuit constants, noise of frequency which is incapable of being removed comes wraparound to the reference voltage output terminal A, power source noise after rising of reference voltage is not necessarily removed sufficiently.
Furthermore, since the load capacitance C.sub.L is connected in between the reference voltage output terminal and the ground, the capacitors C.sub.1, C.sub.2 are necessary to be sufficiently large value such that the load capacitance C.sub.L can be neglected. However, when value of the load capacitance C.sub.L becomes large, there is the problem that it is difficult to realize the capacitors C.sub.1, C.sub.2 on the integrated circuit.